Heat the oil in a large pan and brown the Lamb then transfer to a casserole dish.  In the same pan gently cook the onion, carrot and celery until tender and lightly browned, add 3 cloves of garlic and cook for approximately 1 minute before adding this to the casserole dish.  Add the flageolet beans and the bouquet garni, tip any excess fat from the pan and add the water, stirring to combine the meat’s residue, pour this over the Lamb and season with pepper.  Transfer this to the oven, preheated at 170ºC/325ºF/Gas 3, for 1-1½ hours or until the beans are tender but not starting to disintegrate.  Stir in the tomatoes, tomato puree, chilli and sugar and season with salt. (The tomatoes and salt prevent the beans from softening which is why they are not added earlier.  Added at this juncture should prevent the beans from disintegrating.)

Return the casserole to the oven and continue to cook for a further 1-2 hours, stirring occasionally, until the meat is so tender it falls of the phone. Remove the chilli, take a couple of ladlefuls of the beans and juices and blend in a food processor until smooth.  Stir this into the casserole to make a sauce, taste and adjust the seasoning as required.

To make the gremolata garnish, mix the lemon zest, remaining garlic, and parsley together and finely chop the mixture.  Sprinkle this over the casserole to serve.